Corrosion control in two-pass regenerative heater



Aug. 19, 1952 w. D. YERRICK CORROSION CONTROL IN TWO-PASS REGENERATIVEHEATER Filed oct. s. 1949 n l w U. l l El m/f, u; l ...Al l l 4 y MwvwQlu n() y. I a

m f/W/ /20 Am 01m57- Patented Aug. 19, 1952 CORROSION CONTROL INTWO-PASSI y REGENERATIVE HEATER v William D. Yerrick, Wellsville, N. Y.,assignor to The Air Preheater Corporation, New York, N. Y.

Application October 8, 1949, Serial No. 120,340

1 Claim.

The present invention relates particularly to improvementsy inregenerative yair heaters of the rotary type and specically tominimizing corl -at the opposite ends of the rotor and the latter isdivided by radial partitions into a plurality of wedge-shapedcompartments in which the heat transfer material in the form of platesis mounted. To prevent mingling of the streams of gas and air thepartitions are conventionally provided with sealing members which bearagainst the opposing faces of the sector plates to seal the gas and airpassages from each other.

The present invention contemplates dividing the rotor into inner andouter annular sections and providing speci-al damper controlled ducts sothat all of the heating gas at low loads may be directed over only partof the heat exchange material which, however, is adequate to heat thelesser volumes of air required. Another object is to provide a simplearrangement for tempering the stream of hot primary air at high loads.

One feature of the present invention is a heat exchanger construction inwhich the effects oi corrosion on certain sections of the heat transferplates due to cooling by the gases is minimized.

Other features and advantages of the present invention will becomeapparent upon consideration of the following detailed description of anillustrative embodiment thereof when read in conjunction With theaccompanying drawing in which:

Figure 1 is a sectional elevation of a Ljungstrom type preheaterembodying the present invention;

Figure 2 is a plan view corresponding to Figure l; and y Figure 3 is afragmentary view on an enlarged scale illustrating a sealing device.

In the drawings the numeral I0 designates the preheater housing withinwhich is mounted a rotor designated as a Whole by the numeral II adaptedto be slowly rotated Within the housing on its axis I2 by a motor I3operating through reduction gearing. Conventionally the rotor I Iconsists of a cylindrical shell I4 connected by radial partition platesI5 to the rotor post I2.

2 The radial partitions divide the interior of the rotor intowedge-shaped compartments each of which contains a multiplicity ofspaced metallic plates I 6 which absorb heat from hot gases passedthereover and then impart it to` air or other fluid to be heated.

Ordinarily the heating gases and the air to be heated flowcountercurrent to each other at opposite sides of the axis I2 of therotor, being admitted to and taken from the housing I0 through ductsconnected into openings in the end plates 20 mounted on the housing -I0at opposite ends of the 'rotor as indicated in Figure 2. According tothe present invention the rotor II is provide-d at a point inwardly ofthe shell I4 with a c1rcular partition 29 which divides the rotor intoinner and outer annular sections 25, 26 radially spaced from each other.Partition 29 is positioned at a radial location such that the'low areais substantially the same in the inner and outer sections, or somewhatgre-ater in the latter to accommodate larger volumes of hot gas andheated air. On the upper end edge of this circular partition there aremounted circular sealing strips 21 which cooperate with a similar strip28 (Figure 3) depending from the under side of the end or sectorplateopposite the top end of the rotor. A special end plate 20 takes theplace of the usual sector plate at the upper end of the rotor, beingformed with an aperture 2I at the outer side of partition 29 and abovesection 2`6 of the rotor to provide for the admission at the upper endof the rotor of hot gases supplied through a duct 22-connected to theupper end of the housing I0. Beneath the rotor I I an extension 23 ofthe housing I0 forms a chamber 24 so that gas iloWing downwardly overthe heat exchange plates I6 in the outer section 26 of the rotor maypass around the lower end of the circular partition 29 and reversing itsdirection iiow upwardly over the heat exchange plates in the section 25of the rotor to be discharged through an opening 30 in the end plate 20into a gas outlet duct 3| suitably connected to the upper end of thehousing inwardly of the gas inlet duct 22 and between the latter and therotor post I2.

The air side of the heat exchanger is of gen? i mary-:air Y outlet 38.

thedual outlet ducts V3'1 (Fig. 2) connectinginto the ends of chamber 36while primary air is diverted through a branch duct 38.

The sector plate 2GB opposite the lower end of the rotor has only a pairof apertures, one each on the gas and air sidesfand separated-by theusual imperforate portion against which the radial seals I9 bear.

A conduit 40' connects the gas inlet duct 22 directly with chamber 24beneath the rotor and thereby forms a by-pass around the outer section26 of the rotor on the gas.

At low'loads of a boiler with which the apparatus is used the damper 4|is closed and the damper i2 opened so that a larger volume of gas may owover the inner section 25, which is in effect the "cold end section, andmaintain the heat transfer plates I at a temperature above the dew pointof the gases. This is further facilitated by provision ofV a vduct 45connecting the air side chamber 33 directly with the pri- Dampers 4'6and 4'! in ducts 38 and :45 are respectively closed and opened atlow'loads so that the outer section 2liV of the rotor is not exposed tolarge volumes of rela-jtively cool air at low loads.

The duct i5 performs the ancillary function of making it possible to mixquantities of rela- 4tively cool air from chamber 33 with the volume 'ofprimary air heated to high temperature at high loads so that temperingof the yprimary air y stream may be effected. v

Y WhatI claimis:

In a regenerative air preheater having a housing containing a rotorturning about an axis centrally located therein, circular partitionmeans dividing the rotor into inner and outer annular sections, heattransfer material carried in said sections, inlet and outlet ducts for aheating, gas connected` to said housing at one end 4thereof at one sideof vthe rotor axis and communicating respectively with `the inner andouter sections of said rotor,and meansvforming `a'chamber at theopposite end of said housing in'communication with both the inner andouter sections of said rotor at said one side of its axis so that theheating gas may flow in series through said sections; a duct connectingsaid gas inlet duct with said chamber and forming a bypass around saidouter section; dampers in said gas inlet duct and in said by-passadapted to apportion the ow cf gas therethrough for maintainingl theheat transfer material in said inner secticmv at'atemperature above thedew-point of said heating gas; inlet Vand outlet ducts for air connectedto said housing at the opposite side ofthe rotor axis; means forminga--second "chamber interconnectingv said inner and outer A ried thereinat a temperature above the dewtained. `Inasmuch as the depth of thesurface insection 25 is reduced by about one half compared withthat ofthe'conventional heater, it is possible to vobtain higher heat recoveryfrom the gases at low loads without the risk of cooling the the dewpoint.

plates I6 in section 25 to a temperature below point of the heatinggases.

r WILLIAM D. YERRICK.

REFERENCES CITED ,The following references are of record inthe file ofthis patent:

UNITED ySTATES PATENTS Number Namek Date 1,781,303 Rydmark Nov. l1, 19302,480,277 Yerrick Aug. 30, 1949 p FOREIGN PATENTS Number Country Date587,085 Great Britain V Apr. 11, 1947

